The present invention relates to an apparatus for switching the operation of a charge valve of an internal combustion engine according to the main concept of the principal claim.
A reduction in the consumption of combustion fuel has, in recent times, assumed increasing importance. One possibility to thus reduce combustion fuel consumption, offered in connection with multiple cylinder motors, is the timed placement out of service of individual cylinders, whereby the remaining cylinders operate with a higher average pressure and, thereby, a reduced specific fuel consumption. To place a cylinder out of operation, not only an interruption of the combustion fuel delivery is required; as well, the charging flow to the corresponding cylinder must also be deliberately interrupted, in that the one or more charging valves, especially the inlet or intake valves, of the respective cylinder are placed out of operation.
A further, important development goal lies in the reduction or decrease of the pollutant content in the exhaust gasses. The starting points for such improvements are to be found in the valve opening functions which are accommodated to the respective operational ranges, whereby optimal combustion conditions can be achieved.
In view of the above-noted reasons, there is a strong need for an adjustable or, respectively, convertible valve operating apparatus.
DE 19 82 8945 A1 discloses an apparatus for the activation and complete de-activation of a charging valve. In connection with this apparatus, the retention of a coupling lever, whose position determines the activation or de-activation of the valve, is effected by means of an electro-magnet disposed in a motor housing or on the cylinder head. In total, this known apparatus requires modifications of the motor housing or the cylinder head, in order to be subsequently installed thereon at a post-engine manufacturing time.
EP 0 016 068 describes an apparatus for converting the operation of a charging valve of a combustion powered engine, which works with a swing lever and a contact lever disposed in contacting relation with the swing lever. A spring, which presses the contact lever into a following disposition on the camshaft, is supported between the swing lever and the contact lever, so that, in this regard, no modification of the cylinder head via a subsequent installation effort is required. The actuation and retaining apparatus for actuating the coupling member is, however, configured as a hydraulic cylinder mounted on the cylinder head or, respectively, the motor housing, the hydraulic cylinder having a tappet which engages a contact surface of a coupling lever which is secured in a non-rotating manner with the coupling member, so that a friction contact occurs between the tappet and the contact surface. The arrangement according to EP 0 016 068 requires, in total, considerable installation room and is, especially because of the hydraulic cylinder, not capable of being subsequently installed on the cylinder head without a necessary modification thereof.
EP 0 995 885 A2 describes a valve actuating mechanism with an outer swing lever for engagement with a cam during the high stroke thereof and an inner swing lever for engagement with a cam during a lower stroke thereof. The ends of the swing lever disposed adjacent the charge valve of a combustion engine are connected to one another via connecting taps. On the other ends of the swing lever, a locking mechanism is provided, which comprises a pin which is movable back and forth between a locking position and a release position.
DE 37 01 480 A1, which describes the state-of-the-art apparatus which is improved upon by the apparatus of the present invention describes a valve actuating system in which the spring which biases the contact lever in the direction of a disposition of the contact lever onto the cam is supported on the cylinder head. This means that an available cylinder head for the subsequent installation of the valve actuating system must be modified, which is expensive. Moreover, a hydraulic cylinder with a tappet is provided for the release, or respectively, the blocking, of the movement which is translated between the contact lever and the swing lever, with the hydraulic cylinder being provided with hydraulic fluid via a hydraulic element on which the swing lever is supported and the swing lever requiring bores, which are expensive to provide, for permitting passage therethrough of the hydraulic fluid.
The present invention inventively provides a solution which advances the state-of-the-art apparatus, in that it has a simple configuration for a conventional combustion engine and can be installed thereon with the least possible modification while providing a high measure of operational reliability.
In accordance with the present invention, the spring which biases the contact lever in a direction into a disposition of the contact lever on the valve cam extends directly between the swing lever and the contact lever so that, in this regard, no modification of the cylinder head is required.
Furthermore, the respective movement of the coupling member of the apparatus into its first and second positions is deliberately and synchronously effected by the rotation of the camshaft, so that the coupling member need only be retained in its second position. This permits a simple configuration of the retaining apparatus.